Enhancing the stability of trinickel molecular wires and switches:: Ni36+/Ni37+

This paper describes in detail four new compounds that contain extended metal atom chains (EMACs) of three nickel atoms wrapped by either di(2-pyridyl)amide (dpa) or the new homologous ligand with an ethyl group at the para position of each pyridyl group, depa, and compares them to the precursor Ni-3(dpa)(4)Cl-2 (1) and the oxidized and rather unstable Ni-3(dpa)(4)(PF6)(3) (2). The new molecules are Ni-3(depa)(4)Cl-2 (3), Ni-3(depa)(4)(PF6)(3) (4), [Ni-3(dpa)(4)(CH3CN)(2)](PF6)(2) (5), and [Ni-3(depa)(4)(CH3CN)(2)](PF6)(2) (6). These compounds are fully described as to preparation, elemental composition, structure, infrared spectra, H-1 NMR spectra (where possible), electrochemistry, magnetic susceptibility, and an EPR spectrum for 4. The effects of (a) introducing the ethyl substituents; on the ligands, (b) replacing axial anions by neutral axial ligands, and (c) oxidizing the Ni-3 chains are reported and discussed. The point of major interest is how oxidation profoundly alters the electronic structure of the EMAC.